A lot of assumptions being thrown around here.
One game does not make him better than Randle. Randle was more consistent overall than Bryce Cotton this season. Randle did not have the kind of supporting cast Cotton had to have success in the playoffs. It might be your opinion that Cotton is better than Randle, but it isn't by any means a self evident fact.
As for "but if Randle stayed", Randle's situation has not been sorted out yet. The 36ers offered him a multi-year deal, and so have Zalgris. Randle says he loves Adelaide; and I guess we'll see how that pans out. Also, why would Randle staying make Cotton stay? I don't understand that.
To say Cotton is too good for this league is to have a pretty low opinion of the league. If the league can pay for him, and if he is not outclassing everyone week in, week out, he is not too good for this league. He is a very good player in this league, however. But is he so much better than our other import point guards to say he is 'too good for this league'? I'd say he is just a symptom of the type of talent we can now bring here on a regular basis.
As for Cotton coming back or otherwise, he seemed to buy into the team and what it stood for. He likes the team chemistry and he likes his teammates. If the Wildcats can offer him a good salary, and if he isn't snapped up by the NBA on something half decent, I think there is a hope of him coming back. He's experienced Europe when he went to Turkey and then he opted out of that contract to go to the cats.